Clever Geek Handbook

MVVM和适配器中的选择项-基本适配器

因此，我终于有了一个库，该库包括从适配器的列表中选择项目的逻辑。经过一个独立于平台的解决方案和一个基于LiveData的库之后，我写了一些东西来帮助您快速轻松地将所有这些链接到适配器，以减少总体代码。



选择ListAdapter接口



让我们从为具有常规线性列表的适配器添加的简单SelectingListAdapter接口开始。根据我的经验，大约90％到95％的适配器都以这种形式出售。



interface SelectingListAdapter<T> {
    fun setListItems(items: ArrayList<T>)
}


没什么复杂的-只需更新项目列表即可。而且，在我看来，将这个接口添加到您的适配器中实现的接口列表并不难。做什么的？为了能够使用这两种扩展方法，我将在下面提到：



fun <T> SelectingListAdapter<T>.observeItemsChange(lifecycleOwner: LifecycleOwner,
                                                   liveDataSource: LiveDataSource<T>) {
    liveDataSource.allItems.observe(lifecycleOwner, { items -> setListItems(items) })
}


该方法observeItemsChange订阅对中项目列表的更改LiveDataSource。



fun RecyclerView.Adapter<*>.observeSelectionChange(lifecycleOwner: LifecycleOwner,
                                                   liveDataSource: LiveDataSource<*>) {
    liveDataSource.observeSelectionChange(lifecycleOwner) { position, _ ->
        notifyItemChanged(position)
    }
}


该方法observeSelectionChange已经订阅了项目选择中的更改。此处仅通知该元素需要更新。下面将说明检查该项目是否已被选择。



fun <T, TAdapter> TAdapter.observeAllChanges(lifecycleOwner: LifecycleOwner,
                                             liveDataSource: LiveDataSource<T>)
        where TAdapter : RecyclerView.Adapter<*>,
              TAdapter : SelectingListAdapter<T> {
    observeSelectionChange(lifecycleOwner, liveDataSource)
    observeItemsChange(lifecycleOwner, liveDataSource)
}


好吧，如果您想一次调用这两个方法，则observeAllChanges可以在一行中完成一个方法。



BaseSelectingListAdapter类



, LiveDataSource, . , :



abstract class BaseSelectingListAdapter<T, VH: BaseSelectingListHolder<T>> 
        : RecyclerView.Adapter<VH>(), SelectingListAdapter<T> {
    var callback: SelectingListAdapterCallback? = null
    ...
}
abstract class BaseSelectingListHolder<T>(itemView: View) : RecyclerView.ViewHolder(itemView) {
    abstract fun bindItem(item: T, isSelected: Boolean, onClick: (() -> Unit)?)
}


, SelectingListAdapterCallback.



interface SelectingListAdapterCallback {
    fun isItemSelected(position: Int): Boolean
    fun clickItem(position: Int)
}


, , , .

BaseSelectingListAdapter , LiveDataSource.



fun <T> setCallback(liveDataSource: LiveDataSource<T>) {
    callback = object : SelectingListAdapterCallback {
        override fun isItemSelected(position: Int) =
            liveDataSource.isItemSelected(position)
        override fun clickItem(position: Int) {
            liveDataSource.clickPosition(position)
        }
    }
}


BaseSelectingListAdapter — , .



    fun fullyInitialize(lifecycleOwner: LifecycleOwner,
                        liveDataSource: LiveDataSource<T>) {
        observeAllChanges(lifecycleOwner, liveDataSource)
        setCallback(liveDataSource)
    }


fullyInitialize, . . , , .



onCreateViewHolder bindItem. -, boilerplate .



class MyAdapter : BaseSelectingListAdapter<User, MyHolder>() {
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) =
        MyHolder(...)//create your holder view
}
class MyHolder(itemView: View) : BaseSelectingListHolder<User>(itemView) {
    override fun bindItem(item: User, isSelected: Boolean, onClick: (() -> Unit)?) {
        //bind your data
    }
}




, . - , , :



  1. .
  2. ( , ), SelectionManager'.




:





Gradle中的链接：



implementation 'ru.ircover.selectionmanager:core:1.1.0'

implementation 'ru.ircover.selectionmanager:livesource:1.0.1'

implementation 'ru.ircover.selectionmanager:selectingadapter:1.0.0'



More articles:


All Articles